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Radiant Cooling/Chilled Beam Systems
Radiant cooling technology is about as old as radiant heating but has been less successful in implementation due to the complication of managing condensation and it was not until the 1960s, with the advent of the general use of suspended office ceiling systems, that commercial-oriented radiant cooling systems were attempted as standardized products. It has never reached domestic use. In recent years, however, the competition among commercial developers to attain LEED status for their buildings has resulted in a resurgence of this technology in a new variant; the Chilled Beam system. The sudden popularity of this technology is based on its much greater energy efficiency compared to conventional central air conditioning, Radiant cooling works similarly to hydronic radiant heating with the difference being that chilled water cooling tubing elements are placed in a ceiling space rather than under the floor and thus causes a convection air flow driven by the sinking cooler air. Typical systems have been based on registers that fit into the framing of the conventional suspended office ceiling in a manner similar to Mini-Split air conditioning registers. However, unlike Mini-Split registers, these units usually lacked any integral fans and relied on convection and/or low velocity above ceiling forced air ventilation systems. These early systems tended to have limited practicality because they were passive and very prone to high volumes of condensation, which even if drained away as with condensation in Mini-Split registers, could contribute to mold in the ceiling space because the systems were so large in area. Earlier building ventilation systems did not operate at positive pressure and tended to have limited ability to control humidity. And, of course, until quite recently most home had no active ventilation at all. Chilled Beam systems integrate radiant cooling elements into an outlet for a forced air ventilation system, employing the coanda effect to create a local room recirculation of air through the cooling coils independent of the larger building air circulation cycle. They rely on modern computer controlled forced air ventilation systems to control dew-point conditions by positive pressure and active dehumidification at the Air Handler Unit in order to minimize or eliminate condensation at the Chilled Beam unit. The chief advantage of the Chilled Beam is energy efficiency -with cooling the more expensive aspect of air conditioning, particularly in commercial buildings with their high solar gains through large windows and high generation of heat from large inhabitant densities and large volumes of modern computer and electronic equipment. Water is a more efficient medium of thermal energy transfer than air. By moving the source of cooling closer to the room and managing the temperature of each room independently a much higher energy efficiency is achieved than possible by cooling from a central point in a building and conveying it by air. The Utilihab Chilled Beam system is based on register units sized according to the standard ceiling grid dimensions. They are designed in two basic types to integrate with the primary plenum and smaller distribution tubing of the Mini-Duct High-Velocity HVAC system. The smaller low profile unit is designed for corner and perimeter ceiling panel installation and takes the place of a conventional outlet port on small distribution tubing. Several would be used in a large room and this is the only type suited to buildings based on the light Primary profile framing -though in general such structures may be better served by Mini-Split systems. It is an adaptation of the Utilihab Mini-Split ceiling register. The large area register is designed for central and perimeter ceiling positions and integrates to the primary plenum tubing in the HVAC network. It may be several meters long. One of these registers will typically handle a fairly large room. Utilihab Chilled Beam units must be combined with active dehumidification in the Air Handler Unit of the Mini-Duct HVAC system and active dew-point monitoring by its microcontroller. This is necessary as the units rely entirely on this to prevent condensation.